Virulence Plasmid (pYV)-Associated Expression of Phenotypic Virulent Determinants in PathogenicYersiniaSpecies: A Convenient Method for Monitoring the Presence of pYV under Culture Conditions and Its Application for Isolation/Detection ofYersinia pestisin Food

Abstract

InYersinia pestis,Y. pseudotuberculosis, andY. enterocolitica, phenotypic expression of virulence plasmid (pYV: 70-kb)-associated genetic determinants may include low-calcium response (Lcr, pinpoint colony, size = 0.36 mm), colony morphology (size = 1.13 mm), crystal violet (CV) binding (dark-violet colony), Congo Red (CR) uptake (red pinpoint colony, size = 0.36 mm), autoagglutination (AA = cells agglutinate), and hydrophobicity (HP = clumping of cells).Y. pseudotuberculosisis chromosomally closely related toY. pestis;whereas,Y. enterocoliticais chromosomally more distantly related toY. pestisandY. pseudotuberculosis. All three species demonstrate Lcr, CV binding, and CR uptake. The colony morphology/size, AA, and HP characteristics are expressed in bothY. pseudotuberculosisandY. enterocoliticabut not inY. pestis. Congo red uptake inY. pestiswas demonstrated only on calcium-deficient CR magnesium oxalate tryptic soy agar (CR-MOX), whereas this phenotype was expressed on both CR-MOX and low-calcium agarose media inY. pseudotuberculosisandY. enterocolitica. These phenotypes were detectable at 37°C within 24 h inY. enterocoliticaandY. pseudotuberculosisbut did not appear until 48 h inY. pestisdue to its slower growth rate at 37°C. The pYV is unstable (i.e., easily lost under a variety of culture conditions) in all three species but is more unstable inY. pestis. The specific CR uptake byY. pestisin CR-MOX and the delayed time interval to express Lcr and CR uptake provide a means to differentiateY. pestisfromY. enterocoliticaandY. pseudotuberculosis. These differences in pYV expression inY. pestiscan be used for its isolation and detection in food.